The present invention relates to disc drive data storage systems. More specifically, the present invention relates to methods and apparatus for performing a seek in a disc drive data storage system.
A disc drive data storage system includes a data storage disc providing a disc surface that has concentric data tracks, a data head that can read/write to the disc surface, and an actuator which supports the data head above the disc surface. Movement of the actuator causes movement of the data head.
In disc drives, an access can be defined as the movement of the data head relative to the disc surface from the end of one read/write on the disc surface to the beginning of the next read/write on the disc surface, but not including the actual reading/writing. The access time is made up of two time components: seek time and latency time. The seek time component is the time taken to travel from the track on which one read/write completes to the track on which the next read/write begins. The second time component, the rotational latency time, is the time the disc drive spends waiting for the appropriate data to rotate under the head after the head has arrived at the track on which the next read/write begins. The rotational latency time can be a significant part of the access time for all but the longest seeks. It is the dominant component of the access time for relatively short seeks. In some prior art disc drive data storage systems, commands sent by a host computer are executed in an optimum order to minimize both radial movement of the data head and also rotational latency.
In spite of the advantages gained by optimizing the execution of commands, lack of control over the number of commands and the time between commands arriving from the host computer imposes limitations in the optimization techniques. Thus, significant rotational latency still exists in current systems.
Access operations are typically a combination of rapid movement of the actuator that moves the data head to the desired track followed by a wait period for the appropriate data to come under the head. Rapid movement of the actuator causes problems in the disc drive data storage systems such as increased vibration, an increase of emitted acoustics, high power consumption, and generally a higher stress factor to the overall mechanics.
The present invention provides a solution to these and other problems, and offers advantages over the prior art.
The present invention relates to disc drive data storage systems which reduce vibrations, acoustics and/or power consumption without increasing access times.
In accordance with one embodiment of the present invention, a seek method of controlling an actuator to move a data head includes determining a first rotational position corresponding to a rotational position of the data head when the seek will start and determining a second rotational position corresponding to a rotational position of the data head at a destination of the seek. An access time required to move the data head from for the first rotational position on a current track to the second rotational position on a destination track, using a fastest of multiple seek profiles, is determined. Subsequently, a slower or slowest of the multiple seek profiles which can be used to move the data head from the current track to the destination track, within the determined access time, is determined. The slower seek profile can be the slowest of the multiple seek profiles which can move the data head within the access time. The actuator is then controlled by using the determined slower or slowest of the multiple seek profiles to move the data head from the current track to the destination track.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.